objects not showing up in outliner
You have only one object in this scene, and all these shapes are part of that same object. You probably added each new mesh in Edit Mode, instead of Object Mode.

When you add a new mesh primitive while in edit mode, the new primitive is added into the same object you are in the process of editing.

Since the name of the object is "Cylinder", I assume you created the cylinder first, then added the other shapes while editing the cylinder.

You can see that this has happened since all 3 meshes are editable when you are in edit mode. Normally, when meshes are separated into different objects, you can only edit one at a time: